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Old 05-19-2008, 11:16 PM   #1
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Registered: Nov 2004
Location: norway
Distribution: gentoo
Posts: 23

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iptables -t raw [conditions] -j TRACE is not logging

Host description
distro: gentoo 2007.0 amd64 
kernel: linux 2.6.23-gentoo-r8
ntfltr: iptables v1.4.0
logger: syslog-ng 2.0.6
Problem description
iptables TRACE target never gives any output through ipt_LOG and syslog-ng
I have successfully configured masquerading on the gateway with stuff like browsing, counter-strike:source, azureus and samba/nfs working behind it. To account for my lack in experience with netfilter I've set up logging through both ipt_LOG and ipt_ULOG to monitor dropped and rejected traffic. This has gotten me pretty far, but now I'm stuck. That is, I need more diagnostics/debugging over the netfilter rules.

I installed the latest iptables package which supports the -j TRACE target. The kernel has support for this too. I can actually run
iptables -t raw -A PREROUTING -p tcp --dport 80 -j TRACE
iptables -t raw -A OUTPUT -p tcp --dport 80 -j TRACE
without errors about illegal/missing chains/targets/matches.
Logging through syslog-ng and ulogd works because I see stuff like
May 20 04:07:46 raptor a   ping  IN=eth0 OUT= MAC=00  SRC= DST= LEN=84 TOS=00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=1906 SEQ=5
May 20 05:33:10 raptor a   loop  IN=lo OUT= MAC=00  SRC= DST= LEN=80 TOS=00 PREC=0xC0 TTL=64 ID=16564 PROTO=ICMP TYPE=3 CODE=3
in my ulogd [LOGEMU] file and
05 20 04:06:43 tryggve kernel TRACE target: only valid in raw table, not filter
05 20 04:08:20 tryggve kernel a  Lping IN= OUT=eth1 SRC= DST= LEN=84 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=1906 SEQ=1
in /var/log/messages. (Dont mind the TRACE error above, I was using -t filter.)
The expected behavior of -j TRACE is do dump iptables rules a given packet goes through to syslog. Surprisingly i get nothing even when specifying port 80 traffic to be TRACEd.

If anyone has made this work for them I am very curious as to how they did it. If you want to have a look at my kernel .config or syslog-ng.conf or anything else on my system don't hesitate to ask, but I can't imagine the problem is rooted in the configs.


debugging, diagnostics, firewall, gateway, iptables, netfilter, network, trace

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